Like i said before. They will all serve your purpose just fine. It all depends on the games as that is the only thing that you will be doing that is CPU intensive. Higher is always better in that respect
By the way if you're surfing with 10-15 windows at a time you might find the "Tabbed Browsing" feature of FireFox or Opera a useful addition to your daily life. And as far as IE and noticing the difference between HT and non HT..... you'd be hard pressed to find a noticable difference if any at all.